In fixed intervals? I'm not so sure about that. Generally if the intervals are fixed, you shouldn't need delimiters, you know where one thing begins and another ends anyway.

Anyway, BWT-based compressors like Bzip2 do a good job on "repetition, but with random differences". Better than LZ-based compressors. However, they are not competitive on speed, and it's gotten relatively worse as computers got faster since the Burrows-Wheeler transform can't be parallelized very well and is inherently cache-unfriendly.